Charging System Voltage Too High

WHEN MONITORED
With the ignition key on and the engine running for 3 minutes.


SET CONDITION
Voltage output does not decrease when the PCM attempts to reduce generator field current and there are no detected field problems.

THEORY OF OPERATION
The generator field voltage is varied by the PCM to maintain a system target or "control" voltage of between 12.9 volts and 15.0 volts.

- If the voltage sensed at cavity 3 of the PCM connector is less than the control voltage, the PCM supplies more ground to the field circuit, (allowing more current to flow).

- If the sensed voltage is more than the control voltage, the PCM supplies less ground to the field circuit, (allowing less current to flow).

Control voltage is determined by the PCM by continuously monitoring the voltage sensed at PCM cavity 3 and the battery temperature sensor or ambient sensor input while the engine is running.

POSSIBLE CAUSES
- Generator Internal Short
- Generator Field Driver Short To Ground
- PCM Failure